Molding mechanism



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Patented Apr. 6, 1954 MOLDIN G MECHANISM Edward Van der Pyl, Holden,

Norton Company, Wor

tion of Massachusetts Application April 11, 1951, Serial No. 220,475

8 Claims. l The invention relates to molding mechanism particularly for the molding of grinding Wheels, especially medium or large sizes of grinding wheels.

One object of the invention is to provide auto- Y matically operating mechanism to ll a mold and evenly to distribute the material to be molded therein. Another object of the invention is to provide a continuously acting mechanism producing grinding wheels in a green uniform density throughout. Another object of the invention is to provide a mechanism for charging the mold in an automatic press whereby to obtain well molded grinding wheels with very few or no defective ones, in the course of production of scores or even hundreds thereof. Another object of the invention is to provide a mechanism which will successfully make very perfect grinding wheels of large size in a very minimum of time for the manufacture of dozens, scores or hundreds of wheels.

Other objects will be in part obvious or in part `pointed out hereinafter.

Inthe accompanying drawings in which is shown one of many possible embodiments of the mechanical features of this invention,

Figure 1 is a front elevation, certain parts being shown in section, of a molding press with which the mechanism of the invention is used and certain parts of which constitute part of the mechanism of this invention,

Figure 2 is an hydraulic diagram showing a solenoid and valves and a piston and cylinder unit vfor actuation of a mold charging box, and a wiring diagram,

Figure 3 is a cross-sectional view of a piston and cylinder unit for the actuation of a hopper gate, illustrating also pneumatic connections, and a wiring diagram,

Figure 4 is an hydraulic diagram illustrating various solenoids, valves and pipe connections for the automatic operation of the press of Figure 1 which is an hydraulic press,

Figure 5 is a wiring diagram,

Figure 6 is an elevation of a piston and cylinder unit and connections to operate the charglng box.

Figure 7 is a sectional 11 of Figure 6,

Figure 8 is a sectional 8-8 of Figure 6,

Figure 9 is a view partly in elevation and partly in section of ari adjustable controlling mechanism located at the upper part of the press,

Figure 10 is a sectional view taken on the line la-I0 of Figure 9,

view taken on the line view taken on the line state of f' Mass., assigner to cester, Mass., a corpora- Figure 11 is an elevation of a control located near the bottom of the press,

Figure 12 is a sectional view taken on the line |2-I2 of Figure 11,

Figure 13 is a plan view and the hopper therefor,

Figure 14 is a sectional lil-I4 of Figure 13,

Figure 15 is an enlarged fragmentary detail of the bottom of the charging box,

Figure 16 is an enlarged fragmentary view partly in section and partly in elevation of the mold and the bottom of the charging box at a particular instant during the mold lling,

Figure 17 is a view similar to Figure 16 showing the parts immediately after the mold has been lled,

Figure 18 is a View similar to Figure 16 but illustrating the action when certain adjustments are changed so that the mold bottom plate does not descend until the charging box has moved over it,

Figure 19 is a side elevation of a system of hoppers whereby to supply the apparatus with the material to be molded,

Figures 20 to 27 inclusive are detailed crosssectional views of various valves and other fluid pressure apparatus.

Many of the parts and mechanisms herein illustrated and described are illustrated and described in some cases more fully in a copending application Serial No. 30,174, led May 29, 1948. So far as possible the numerology of this application is the same as that of the aforesaid copending application.

Referring first to Figure 1, the press comprises a massive bed plate |09 which rests upon a concrete foundation ll having a well m2 with a shoulder I 03. An annular cover plate Ilo may be provided for the well |02 to keep dirt and tools out of the well and to provide a footing for the operator.

Extending through the bed plate I 00 are a plurality of massive rods lll, three being a preferred number. These rods lll are threaded at the bottom and fitted with nuts H2 under the bed plate lill). The rods Ill near their upper ends have collars i3 secured thereto and the rods extend through a massive cap H4 which is supported by the collars H3. The rods IH are also threaded at the top and fitted with nuts H5 above the cap H4. The rods lll with the nuts IIZ and H5 thus hold the bed plate I and the cap H4 from moving apart under the reactive force developed in operating the press.

of the charging box gate and actuating mechanisms view taken on the line Between the bed plate and the cap ||4 is a massive mold table through which the rods extend and in which the pressing is done. This mold table |20 rests on sleeves |2| surrounding the rods and extending to the bed plate |00. On the upper side the table is held down by collars |22 on the rods Still referring to Figure 1, the mold ta-ble |20 has extending therethrough a large cylindrical bore |25 in which is secured a mold band |35. I shall not herein describe the details of the mounting of the mold band nor of the manner in which the arbor |12 is supported in the mold since these features are thoroughly described in the aforesaid copending application and the present invention is not concerned with the details.

Still referring to Figure 1, extending through the bed plate |00 is a large cylinder |40 having a circumferential shoulder |4| resting on top of the bed plate |00. This cylinder has an internal cylindrical bore |42 in which fits a large piston |43 having integral therewith a massive ram |45. The ram |45 fits in packing |46 which is located in a cylinder head |41 which is located in the upper end of the cylinder |40 in screw threaded engagement therewith. At the upper end of the packing |46 is a collar |50 holding the packing |46 in place, the collar |50 being secured to the head |41 by screws, not shown. This packing |46 constitutes a stuffing box to keep the fluid from escaping. Mounted on and secured to the ram |45 is a ram head |60, which is a massive circular plate. In the mold band |35 is a mold bottom plate |10 having a central hole to receive the arbor |12. This mold bottom plate |10 is removably secured to a pair of steel columns |15. One of these steel columns is illustrated in Figure 1 and the other thereof is illustrated in Figures 15 and 17; they are located on either side of a diametral member |3| (Figures 16 and 11) which supports the arbor |12. These columns |15 are secured, in a manner fully described in the aforesaid copending application, to the ram head |60.

Referring again to Figure l, supported by the cap ||4 is a large upper cylinder 220 which is coaxial with the cylinder |40. The cap ||4 has a vertical bore in which the cylinder 220 fits and the cylinder 220 has a shoulder abutting the under side of the cap ||4 to take the thrust of many tons when the press is operating. A nut 224 in screw threaded engagement with the cylinder 220 engages the upper side of the cap ||4 and holds the cylinder 220 from falling.

In the cylinder 220 is a piston 225 operating a ram 226 to the bottom of which is attached a ram head 221 which is likewise a massive circular plate. To the under side of the ram head 221 is `detachably secured a mold top plate 235 having a central axial bore into which the arbor |12 may extend during the molding operation. In order to guide the ram 226 in the cylinder 220 and to form a stufng box so that the fluid under pressure which lifts the piston 225 shall not escape, heavy packing 250 is provided in the cylinder 220 and around the ram 226, the packing 250 being held in place by means of a collar 252 secured to the cylinder 220 by means of bolts, not shown.

Still referring to Figure l, secured to the top of the ram head are a plurality (preferably three) of blocks 255 upon each of which are mounted a plurality of cylindrical posts 258 in piled relation, For the purpose of adjusting the apparatus for the manufacture of grinding wheels of different thicknesses one or more posts 258 can be removed from each pile of posts or one or more posts 258 can be added to each pile of posts. Thus collectively the piles of posts 258 constitute gauging means to determine the lower position of the upper ram head 221, whereas the blocks 225 constitute gauging means to determine the upper position of the lower ram head |60. Blocks 255 of different heights can be used for the manufacture of grinding wheels. of different thicknesses. The blocks 255 are larger in diameter than the posts 258 and the latter extend through |bores in the table |20 which barely clear the posts 253 so that the blocks 255 can engage the under side of the table |20.

Referring now to Figures 13 and 14, I provide a charging box 300 the shape and movement of which relative to the mold plate |10 is one of the features of this invention. However, the construction and shape of this charging box will be hereinafter described. A hopper 36|, only a portion of which is shown in Figure 14, contains a supply of particles which collectively constitute a free-flowing dry granular mix. For the manufacture of grinding wheels each particle may consist of an abrasive granule coated with an envelope of bond of particle size very much smaller than that of the abrasive granules and preferably mixed with wax. The apparatus of this invention can be used automatically to mold vitried grinding wheels or on the other hand it can be used automatically to mold resinoid bonded grinding wheels. For an illustrative embodilnent of the kind of mix which this apparatus is capable of handling, see U. S. Letters Patent No. 2,534,128, granted December 12, 1950, on application of Wallace L. Howe.

The hopper 30| is shown as supported by a ring 302 having a countersunk portion to receive the hopper; connected to and depending from the ring 302 is a tube 303 having an integral boss 304 extending from one side thereof, the boss 304 having a vertical bore therethrough, receiving bearings 305 journalling a vertical shaft 306. Pinned to the bottom of the shaft 306 is the hub 301 of a gate 308 in the shape of a disc, which in one position closes the bottom of the tube 303 and in another position opens it.

Pinned to the top of the shaft 306 is a forked arm 3|!) connected by a pin 3|| to a link 3|2 the other end of which is connected to a clevis 3|3 on the end of a piston rod 343 by means of a pin 344.

Referring now to Figure 3, the piston rod 343 extends through a stuffing box nut 345 and through a stufling box head 346 having packing 341 into a cylinder 348 having at the other end a head 349. In the cylinder 348 on the piston rod 343 is a piston 350. A source of air under pressure is connected by a pipe 35| having a hand valve 352 to a T union 353 to which are connected hoses 354 and 355. The hose 354 is connected to a port 355 extending through one end of the lcylinder 340 as shown. The hose 355 is connected to a port 351 in a valve casing 350 which may be integral with the cylinder 348.

Extending the length of the valve casing 358 is a cylindrical valve chamber 350 in which is a valve piston 360 with a reduced diameter portion 36|. The valve piston 360 has a piston rod 362 which extends through a head 363 blocking one end of the valve chamber 359. other end of the valve piston 300 is a spring. 365 which is held in the chamber 353 by a head 366 Contactin*y theI blocking the other end of the chamber 359. A port 361 extends into the chamber' 359 where the spring 355 is located, thus to prevent entrapped air from blocking movement of the piston valve 360. When the piston valve 360 is in the position illustrated in Figure 3, the reduced portion 36| connects a port 310, leading to the outside air, to a port 31| in the casing 353 which is connected to a long passage 312 and then to a port 313 extending to the inside of the cylinder 348 adjacent the head 349. This drops the pressure in the cylinder 348 adjacent the head 349 to atmospheric but at all times when the valve 352 is open (this is lmerely a hand shut-off valve) the port 353 is connected to pressure. Therefore the piston 350 is held by the air under pressure from the line in the position shown in Figure 3 holding the gate 308 in the open position. But when the piston valve 360 under the influence of the spring 365 moves to carry the reduced portion 36| into registry with the port 351, at this time also closing the port 310, air under pressure goes from hose 355 through port 351 by reduced portion 36| through port 31| through passage 312 through port 313 into the cylinder 34B adiacent the head 349 and this forces the piston 350 in the direction of the stufling box 346 thus moving the arm 3 l 0 and closing the gate 363.

Referring now to Figure 13, an arm 311 is connected to the charging box 300 and the de- Y tails of the connection will be hereinafter de1 scribed. The charging box 300 is, by the mechanism about to be described, moved in an arc over a wear plate 389 located on top of the table |20, and in Figure 16 it will be noted that the top of the mold band |35 is flush with the top of the wear plate 389.

The arm 311 has a split hub 400 one part of which is integral with the arm 311 and the other part of which is bolted to the rst part by bolts not shown. This split hub 400 is located on a split sleeve 40| surrounding.r one of the rods and the hub 400 is supported by one of the collars |22. Also connected to the hub 400 is an arm 402 which is connected by a pin 405 to a link 406. Referring now especially to Figure 6, the link 405 isconnected by a pin 401 to a clevis head 408 which is internally screw threaded to receive a screw threaded end 409 cf a piston rod 4|0. A nut 4H rod M0 extends through a cylinder head 4|2 into a cylinder 4|3 where the piston rod 4|0 has a piston 414. Fluid under pressure, preferably hydraulic fluid such as oil, is admitted alternately to opposite ends of the cylinder 4|3 to move the arm 311 and thereby to move the charging box 300 from one position to the other. The cylinder 4|3 is secured in position by means of clamps 4|5 secured by bolts M6 to portions 4|1 of an extension 4|8 bolted to the mold table |20. In this connection the operating parts to charge the mold are omitted from Figure 1 more clearly to show the basic structure of the press as the relationship of the mold charging mechanism to the portions of the press is Well illustrated in Figure 13.

When the press is idle the charging box 300 is under the gate 308 and the charging box contains a mixture of abrasive and bond ready to be molded into a grinding wheel because the gate 309 is open. Incidentally while a grinding wheel mixture flows it doesnt iiow exactly like water no matter. how free flowing it may be. It has an angle of repose and consequently there is nothing incompatible with showing the gate 308 holds these parts together. The piston .d

Y solenoid 430 operates a pilot valve 43| above the top level of the charging box 300 since most position, both as shown in Figure 1. When the operator starts the machine to operate automatically, electrical mechanism, which will hereinafter be described, energizes a solenoid 420 (see now Figure 2), which operates a valve 42|',

which admits uid under pressure from a lowpressure line 422 into a pipe 423 which is connected to a flow controlling valve 424 the other side of which is connected by a pipe 425 to the left-hand side (Figure 6) of the cylinder 4|3. The right-hand side of the cylinder 4|3 is always connected to the low pressure line 422 by means of a pipe 421. The piston 4|4 moves to the right, Figure 6, whenever the pressure is exerted' against its left-hand side because the area of the piston rod 4|0 reduces the effective area of the piston 4|4 on the right-hand side. Thus the chargingr box 300 moves in a counter-clockwise direction, Figure 13, to carry the charge of dry granular mix to a position above the mold band when the solenoid 420 is energized.

Referring 430 is deenergized the ram |45 moves downwardly carrying down the plate |10. This actiontakes place because the deenergization of the which moves a valve 432 allowing fluid from the bottom of the cylinder |40 to exhaust by way of a pipe 433 through the valve 432 and then by way of a pipe 434 to a supply tank. The limited area of the upper side of the piston |43 is at this time under low pressure by way of a pipe 435 which is connected to a valve 436 which at this time connects the pipe 435 to a pipe 431 which branches into a pipe 438 which pressure supply pipe 422.

Thereafter a solenoid 44| is energized which actuates a pilot Valve 442 which moves a valve 443 to admit iiuid under low pressure from the line 422 through a pipe 444 having a check valve 445 and into a pipe 446 which leads to a pipe 441 which leads to the upper end cf the cylinder 220. The limited area of the underside of the piston 225 is always under high pressure by way of a high pressure line 443 having a needle valve 443. The pressure in the low pressure line 422 may be for example 300 pounds to the square inch and the pressure in the line 44S may be for example 2500 pounds to the square inch. However so much greater is the area of the piston.v

225 than the area thereof minus the ram 226 that the lower pressure prevails over the high pressure and of course the considerable weight of the parts is also acting to move them downwardly. The action however forces the high pressure fluid back into the line 448 and the iluiffi must travel through the needle valve 449 so therefore the speed of downward movement can readily be controlled by means of the needle valve 449.

At a time in the cycle of operation which is adjustable but which is generally at the moment when the top mold plate 235 enters the mold band |35, the lower ram 45 is caused to move upwardly while the upper ram 226 continues ,to move downwardly; ultimately both motions to Figures l and 4, when a solenoid leads to the low are stopped by the contacting of the posts 258 with the ram head 221 as already indicated. The motion of the two rams towards each other is at rst under low pressure and the low pressure line 442 transmits fluid in large volume per unit of time. Eventually, however, when back pressure is built up by the resistance of the material being molded, the pressure automatically rises and both rams are thereafter forced towards each other by the full pressure of the line 448. The transfer of actuation from the low pressure line 422 to the high pressure line 448 is not only automatic but takes place without any further shifting of valves. This control gives the double advantage of rapid movement in the early stages.

and high pressure in the later stages in order to compact the material into a strong article. Furthermore, it is achieved with economy of the high pressure fiuid. These actions take place as follows.

At the instant hereinbefore indicated, namely when the mold top plate 235 entered the mold band |35 or just before or just after this event, the solenoid 44| was deenergized, the solenoid 430 was energized and a solenoid 459 was energized. Deenergization of the solenoid 44| shifts the pilot valve 442 to move the valve 443 to disconnect pipes 444 and 446. Energization of the solenoid 459 shifts a pilot valve 45| which shifts the valve 436 to connect the pipe 435 to a pipe 452 which is connected to the pipe 441. At the same time the shifting of the valve 435 shuts off the pipe 435 from the pipe 431, Thus the upper end of the cylinder |49 is now connected to the upper end of the cylinder 229. At the same time the pilot valve 45| itself connects a series of pipes 453, 454, 455 and 456 to a pipe 451 running to a valve 458. The pipe 453 comes out of the low pressure line 422 and thus fluid under low pressure is admitted to the valve 453. This valve 458 is opened when the fluid under low pressure is admitted through the pipe 452' thereby to connect pipes 456 and 463. In the pipe 463 is a throttle valve 45| and the pipe 469 is connected to the high pressure line 443. The pipe 459 is connected to a pipe 462 and when the solenoid 430 was energized, the pilot valve 43| was operated to shift the valve 43?. to connect the pipe 462 with the pipe 433. However, the pipe 438 leading from the low pressure line 422 is connected by means of pipe 463 with the pipe 462, there being a check valve 464 in the pipe 463. Now it will be seen that both high and low pressures are connected to the bottom of the cylinder |46 but the high pressure will not enter the main low pressure line 422 because the check valve 464 prevents it from so doing, and furthermore, the high pressure fluid will not at first take control of the operation because its flow is restricted by the throttle valve 46|. However, when the low pressure can no longer do the job, the -high pressure will. And as the ram |45 moves upwardly, the ram 226 moves downwardly at. the same rate since fiuid is forced by the piston |43 through the pipe 435 to the pipe 452 to the pipe 441 to the upper end of the cylinder 220.

For supplying fluid to the pilot valve 442 there is a pipe 465 connecting the pilot valve 442 to the pipe 453 which is connected to the low pressure line 422. For supplying fluid to the pilot valve 43| there is a pipe 456 connected to the pipe 455 which through pipes 454 and 453 is connected to the low pressure line 422.

When movement of the rams |45 and 226 to- 8. Wards each other is stopped by the contact o! the blocks 258 with the ram head 221, pressure is built up in the system and is carried by a pipe 419 to a piston-cylinder unit 41| which under this extremely high pressure actuates a switch 412 in a switch box 412a. This causes deenergi- Zation of the solenoid 450 and energizes a Solernoid 415. This action moves the pilot valve 45| which moves the valve 433 again to connect the pipe 435 to the pipe 431 and at the same time cuts off the pressure to the pipe 451 thus shifting the valve 458 to disconnect the pipes 459 and 469. Energization of the solenoid 415 operates a pilot valve 4:5 to shift the valve 443 to connect,

the pipe 446 to an exhaust pipe 418. Fluid to suppy the pilot valve 416 comes from pipe 454 by way of a pipe 411. Now the high pressure from the line 448 through the valve 449 can move upwardly the ram 226 and the fluid will exhaust through the pipes 441 and 446 to the exhaust pipe 419 as the piston 225 moves upwardly. At the same time high pressure has been disconnected from the bottom of the cylinder |49 but the low pressure from the line 422 via the pipe pipe 453, pipe 432 and pipe 433 enters the lower end of the cylinder |48 to continue the upward movement of the ram |45 thus carrying the pressed grinding wheel W out of the mold ring E35. The bottom mold plate |10 is stopped right on the level of the p ate 389 by the b colis 255 coming in contact with the table 29, but the rain 326 continues to rise to carry the mold top plate 235 well up out of the path of the charging box 398 when it returns during the succeeding cycle of operation. The press has now completed one cycle. The cycle Lnmediately repeats since the solenoid 420 is reenergized as will be hereinafter explained.

Out of precaution I have provided a relief valve 419 connected to the pipe 435 so that in case the piston-cylinder unit 41| is set to operate at a dangerous high pressure, the relief valve 419 will operate to save the apparatus from a smash. This relief valve 419 is therefore in the nature of a safety valve and the molding press is operable Without it. Naturally the valve 419 should be set to open at a higher pressure than that at which the unit 41| is expected to operate.

The automatic cycle of operation of the molding press is controlled by various limit switches and relays which operate the various solenoids above mentioned. These limit switches are operated mechanically by movement of the various parts. Such mechanisms are shown in Figures 2 and 5 to l2 inclusive. Referring now to Figures 2, 5, 6, '1 and 8, surrounding and secured to the clevis head 468 is a hub 489 having an arm 492 which is secured to a rod 483 that is slidable in bearings 484 and 485 in :brackets 486 and 481 on plates 498 and 499 secured to the extension 4|8. On the rod 433 are dogs 49| and 492 which can be secured in adjusted position thereon. When the charging box 339 is under the gate 308, the piston 4|4 is to the left as shown in Figure 6, and the dog 49| is in contact with the roller 493 of a switch arm 494 of a limit switch 495 in a box 495e. When the charging box 300 moves to a position over the mold band |35, the actuating piston 4|4 has moved to the right, Figure 6, and the dog 492 contacts the roller 491 on a switch arm 498 of a limit switch 499 in a box 499e. The dog 492 moves beyond the roller 491 and eventually engages a roller 580 on a switch arm 50| of a switch 502 in a switch 502e, and it is this action which stops the inward motion of the charg-.v

` a roller 545 on a switch arm 541 ing box 308 and starts it towards the gate 388. I provide a fourth switch box 5831i having therein a switch 583 actuated by an arm 504 having a roller 85 which is depressed by the dog 49|, which is a long dog and never goes beyond the roller 585 to the right thereof. These boxes 495e., 459e, 582e and 583m are adjustably secured to the face of the extension 4I8 by screws 585 in slots 581 in the boxes.

Referring now to Figures 9 and l0, extending through the cap I |4 is a long bolt 5 I 8 surrounded lby a spring 5I I which bears at one end upon the top of the cap ||l| and at the other end against nuts 5|2 adjustably positioned on a threaded end 5|3 of the bolt 5I0. The bolt 5|!) is likewise threaded at its lower end 5I4 and is thereby secured to a shaft 5|5 which is secured to a long bolt 5I6 having an upper threaded end 5I1 and a lower threaded end 5ta. The bolt 5I5 is slidable in a bearing 5|9 in a bracket 520 secured to a heavy sheet metal panel 52| `which is secured to the under side of the cap I|4 as by means of an angle iron 522 and a welding operation. The bolt 5I0 is slidable in the cap ||4 and it will be seen that the entire assemblage of bolt 5I, shaft 5|5 and bolt 5I6 can move-downwardly from the position shown in Figure 9, crushing the spring 5I I, but this assembly cannot move upward beyond the position shown in Figure 9. Upon the threaded end 5I8 of the long bolt 5|6 is a dog 523 in the form of a nut which can be secured in any position of adjustment. Secured to the upper side of the upper ram head 221 is a flat ring 525 which projects beyond the periphery of the ram head 221 as clearly shown in Figure 10. When the ram head moves to its lowermost position, the flat rin-g 525 contacts the dog 523 and moves the assembly of bolt 5|6, shaft 5|5 and bolt 5I8 downwardly. The shaft moving outwardly again 5I5 has a beveled shoulder 521 which will then -Y contact a roller 523 on a switch arm 529 of a limit switch 530 (Figure 5) in a box 538a.

Still referring to Figures 9 and l0, mounted upon the panel 52| is a U-shaped bracket 535 supporting a bearing 535 on one leg of the U and having a hole 531 on the other leg of the U,

through which bearing and hole passes a rod 538 which is movable vertically. The rod 538 likewise passes through a bearing 538 in a bracket 548 secured tothe panel 52 I. A spring 54| around the rod 538 between the legs of the U-shaped bracket 535 contacts a collar 542 fastened to the rod 538 and tends to keep the rod 538 at a low position but can be crushed to permit the rod 538 to move upwardly. The lower end of the rod 538 is threaded as shown at 543 and adjustably located on this threaded end is a nut 544. When the upper ram head 221 is in its upper position, the flat ring 525 is in engagement with the nut 544 and has raised the rod 538 bringing an adjustable collar 545 thereon into engagement with of a limit switch 555 (Figure 5) in a'switch box 558a.

Referring now to Figures 11 and 12, secured to the bed plate |88 is a bracket 555 having a pair of bearing arms 556 and 551 supporting bearings 559 and 550 through which extends a rod 55|. This rod 55| is, like the rod 558 and the combina- `tion of bolts 5|8 and 5|6 with the shaft 5I5,

movable vertically. In the case of the rod 56| gravity is relied upon to keep: it in a downward position. It has an upper threaded end 563 hav- 'ing thereon an adjustable nut 554 in the path of a flat ring 565 like the ring 525, this ring 555 beingsecured to the under side of the lower ramy equally 1'0 head |60 and projecting outwardly from the periphery thereof. Accordingly, when the lower ram head rises, the ring 565 will engage the nut 554 and raise the rod 56|. The lower position of the rod 56| is limited by a collar 586 adjustably secured thereto which will contact the arm 551. To the bottom of the rod 56| is secured a disc 568 which, when the rod 55| is moved upwardly, contacts and raises a plunger 565 to operate a limit switch 516 (Figure 5) in a switch box 518a.

The manner in which the various switches whose actuation is above described control the solenoids which in turn control the valves (as heretofore described) to move the various elements of the molding press, automatically to make, from a suitable mixture of abrasive and bond, pressed green grinding wheels W is disclosed in the wiring diagram of Figure 5. I have found it desirable to use for electrical control two sources of electric current at different voltages, for example I may use 228 volts to actuate relays responsive to the closing of the limit switches and 440 volts to actuate the solenoids responsive to closing of the relay operated contacts. Alterhating current, usually 50 cycles, is readily available everywhere, whereas direct current is not so widely available and consequently utilization of alternating current will be preferred in most factories. This can be single phase. All of the relays, solenoids and othei` devices indicated in Figure 5 can be operated by single phase, 60 cycle alternating current, using respectively 220 E. M. F. and 440 E. M. F., but the electrical mechanism hooked up as shown in the diagram well be operated by direct current at two different voltages. in order to make the wiring diagram easier to understand by avoiding scores of instances of crossing wires, I indicate one side of the high voltage power line 515 by the symbol |--I, the other side of the high voltage line 516 by the symbol and one side of the low voltage line 511 by -I- and the other side of the low voltage line 518 by Referring now to Figure 5, the switch 515 which is closed when the lower ram is up is connected by a wire 58|) to the -I- line 511 and the other side of the switch 518 is connected by a wire 58| to the switch 558 which is closed when the upper ram is up and otherwise is open. The other side of the switch 555 is connected by a wire 582i to the coil of a relay 583, the other end of the coil being connected by a wire 584 to the line 518. When the relay 583 is energized, it closes a switch 585. A wire 585 connects one side of the switch 585 to the line 515 while another wire 581 connects the switcht 585 to the solenoid 420. The other side of the solenoid 42|) is connected by a wire 558 to the line 516. This is the solenoid that sends the charging box 358 from its position under the gate 388 to its position above the mold band |35.

When the charging box 358 has nearly completed its movement in, that is away from the gate 555, the limit switch 493 is closed, this being a normally open limit switch. The switch' 489 is connected by a wire 589 to the I- line 511. The other end of this switch 498 is connected by a wire 558 to the coil of a relay 55|, the other end of which coil is connected by a wire 592 to the line 558. The relay 53| upon being energized closes a switch 583 which is connected on one Side by a wire 534 to the line 511 and on the other side to a wire 555 which branches into wires 535 and 591. The wire 555 is connected to the coil or" a relay 588 the other end of which 1l coil is connected by a wire 569 to the line 518. Thus, when the switch 566 is closed by the relay V59 I, the relay 563 is energized.

This action deenergizes the solenoid 430 which, as will be remembered, when energized holds the lower ram 65 up and therefore when deenergized allows it to move down. Deenergization of the solenoid 5.36 responsive to energization of the relay taires place as follows: A normally closed switch 666 is opened by the relay 558 and this switch 666 has a wire 65| connecting it to the -i--I- line 515 and a wire 662 connecting it to the solenoid 436 the other end of which is connected by a wire 653 to the line 516.

The lower ram having thus gone down remains down even though the charging box 366 returns to its position under the gate 368 thus opening the switch 496 and deenergizing the relay 59|. To this end I provide a holding circuit for the relay 563 as follows: Starting with a wire 664 connectingone side of the switch 530 to the -iline 511, then 'to a wire 665 to a switch 666 which is closed by energization f the relay 59B, then from the witch 666 by a wire 561 to the wire 566 to the relay 568 to the Wire 566 to the line 516. Since the switch 535 iS a normally closed switch, the holding circuit is made and the relay 568 remains energized. This switch 536 is actuated when the mold top plate 235 is approximately entering the mold band |35, but until that time the solenoid 436 remains dcenergized.

Still referring to Figure 5, the switch 562 is a normally closed switch and when the dog 452 moves the roller 56e this switch is opened. This switch 552 is connected by a wire 6|5 to the wire 582 on one side and it is connected by a wire 6|6 to a normally open relay switch 6|1 operated by the relay 583. The other side of the relay switch 6|1 is connected by a wire EIS to the line 511. Thus, even after the lower ram has started down responsive to closing of the switch 499 and resulting in opening of the switch 51|), the relay 583 is still kept energized by means of the holding circuit through the relay switch 6|1 and the normally closed switch 552, but when the latter is opened by action of the dog 492 on the roller 566, the circuit is broken and the relay 583 goes dead and this of course deenergizes the solenoid 426 by opening the relay switch 565 which starts the charging box 366 moving outwardly again and even though, as the result of the withdrawal of the dog 462 from the roller 556, the switch 562 closes again, the circuit is not remade because it includes the relay switch 6I1 which opened the moment the relay 563 went dead. This relay 583 will not be reenergized until both rams are up again thus closing both of the switches 556 and 515.

When the charging box 366 has moved all the way out, the switch 495, which is a normally open switch, is closed. Closing of the switch 465 results in energization of the solenoid 44| which starts the upper ram 226 downward under low pressure. This takes place as follows: The switch 465 is connected by a wire 645 to the line 511. The switch 465 is likewise connected by a wire 646 to a normally closed switch 641 operable by the relay 583. The switch 541 is connected by a wire 648 to a normally open switch 649 which is, however, at this moment closed because it is controlled by a relay 655 which is connected by a wire 65| to the wire 605 on one side and by a wire 652 to the line 518 on the other side. Current from the line 511 A the dog 523 on the threaded end 5I8.

can therefore flow through wire 648 and switch 646 to a wire 653 to a relay 654 and thence vby a wire 655 to the line 518. This energizes the relay 654 which closes a normally open switch 656 which connects a wire 651 from the ---lline 515 to a wire 658 to the solenoid 44| the other end of which is connected by a wire 659 to the line 516. Thus, the solenoid 44| is energized and the upper ram 226 descends.

As heretofore explained, when the mold top plate 235 carried by the ram 226 is about to enter the mold band |35, the switch 536, a normally closed switch, is opened. The exact moment is adjustable by adjusting the position of At the moment or position of parts desired the ilat ring 525 carried by the upper ram head 221 strikes the dog 523, the bolt 5|6 is moved downwardly thus moving downward the shaft 5|5 having the shoulder 521 which action opens the switch 530. This action deenergizes the solenoid 44|, reenergizes the solenoid 436 and energizes the solenoid 450. It has Ahitherto been explained how the solenoids under these conditions direct uid under low pressure to raise the ram |45 and to continue the downward movement of the ram 226 at the same rate as the upper movement of the ram |45. The action takes place as follows: The current can no longer iiow through the wire 65| since the switch 53|) is open. So the relay 650 is deenergized and this causes the switch 649 to open which cuts oi current to the relay 654 which opens the switch 656 which deenergizes the solenoid 44|. So also by the opening of the switch 530 current can no longer flow through the switch 666 so the holding circuit for the relay 538 is broken and the switch 660 closes thus energizing the solenoid 436. The solenoid 450 is connected by a wire 666 to a normally closed switch 66| operated by the relay 650 so now the switch 66| is closed. The other side of the switch 66| is connected by a wire 662 to the l--I- line 515. The other side of the solenoid 450 is connected by a wire 663 to a normally closed switch 564 operated by a relay 665. The other side of the switch 664 is connected by a wire 666 to the line 516. The relay 665 is at this moment deenergized so the circuit is complete through the solenoid 456 and it is actuated.

It has already been explained how, when back pressure is exerted by the material being molded upon the pressume fluid, the high pressure is automatically exerted to compress the material in the mold to the desired density. Ultimately, when the posts 258 Contact the upper ram head 221, the pressure in the pipes including the pipe 410 rises to operate the piston-cylinder unit 41| to close the switch 412. This switch 412 is connected by a wire 610 to the -lline 511 and by a wire 61| to the relay 665. So prior to actuation of the switch 412, the relay 665 is dead thus leaving the switch 664 closed. But when the molding operation is completed and the switch 412 has closed, current ilows from the -lline 511 through wire 610 switch 412 wire 61| to the relay 655 and by a wire 612 to the line 518 thus energizing the relay 665 which opens the switch 664 which deenergizes the solenoid 450. Energization of the relay 665 closes a normally open switch 615 connected by a wire 616 to the -l--lline 515 and by a wire 611 to the solenoid 415 which is connected by a wire 618 to the line 516. Thus when the grinding wheel W is fully pressed, the switch 412 closes energizing the solenoid 415 and deenergizing the'solenoid 450. This causes, as heretofore explained, both rams to rise. The switch 412 automatically opens but this does not deenergize the relay 665 since this relay is provided with a holding circuit. A wire 689 from the -I- line 511 is connected to a holding switch 68| closed by the relay 665 and the switch 68| is connected by a wire 682 which leads to a switch 683 operated by the relay 583. The switch 683 is a normally closed switch, that is when the relay 583 is deenergized. The switch 683 is connected by a wire 684 to the wire 61| which is connected to the relay 665, so once the relay 665 is energized it remains energized so long as the switch 683 is closed. When, however, both rams are up, the switches 510 and 550 are closed and this energizes the relay 583 which opens the switch 693 which deenergizes the solenoid 415 but cannot at this time reenergize solenoid 450 because the switch 530 is closed.

The cycle of operation now repeats thus turning out another pressed green grinding wheel W. The cycle of operation continues to repeat to produce more wheels so long as the hopper 30| contains material and so long as'the press is supplied with fluid under pressure and the power lines 515, 516, 511 and 518 are energized. I provide a double pole hand switch 699 across the lines 515 and 516 for energizing and deenergizing at will all the circuits deriving power therefrom. Similarly I provide a double pole hand `switch 69| across the lines 511 and 518 to energive and deenergive at will all the circuits supplied with power from those lines.

Referring now to Figures 3 and 13, a limit switch 695 is connected bv a wire 696 to the line 511 and this limit switch 695 is connected by a wire 691 to a relay 696 the other ens of which is connected by a wire 699 to the 4 line 518. A switch 190 operated by the relay 696 is connected bv a wire 10| to the i--lline 515 and by a wire 102 to a solenoid 103 which is connected by a wire 104 to the line 5161. This solenoid 103, when energized, holds the Valve piston 366 to the left in the position shown in Figure 3. With the parts in the position shown in Figure 3, the gate 366 is onen. But. when the arm 492 moves away from the limit switch 695, this switch opens, and conseouently the relay 698 goes dead and the solenoid 103 is deenergized. so the spring 365 V moves the valve piston 356 to the right and the air pressure moves the piston 356 to tbe right, Figure 3, which swingsthe hopper gate 368 to the closed position. Thus it will be seen that as soon as the charging box 306 has barely started t move, the hopper gate 368 will be closed but, whenever the charging box returns to its nal Vposition of rest under the hopper the hopper gate 30B is opened. Although closed when the valve 360 is in the position shown, the switches 695 and are normally open so are shown that way.

The construction of the various valves whose positions in the hydraulic circuits are indicated in Figure 4 and whose functions has been hereinbefore described are illustrated in Figures 20 to 27 inclusive. These valves are commercial valves, available on the market, and are not per se the subject of my invention. For that reason and also because the drawings, Figures 20 to 27,

are quite detailed and readily understood by one skilled in this art, I shall make my description of these valves reasonably brief.

Figure 20 illustrates the solenoid 420 and the 'valve 42|. A solenoid core member, not shown,

is connected to operate a valve stem having pistons 14| and 142. The low pressure line 422 is connected to a port while the pipe 423 is connected to a port 141. A channel 148 is connected to an exhaust pipe 149 and to a port 150 (the valve has other ports but they are not used). A spring extending between the stern 140 and a cover 156 on the end of the valve casing normally holds the stem 140 and the pistons 14| and 142 to the right as indicated. In this position the port 141 is connected to the port 150 and so therefore the pipe 423 is connected to the exhaust pipe 149. At this time the line 422 is connected to nothing by way of this valve. When, however, the solenoid 420 is energized, the valve stem 140 is shifted to the left and this connects ports 145 and 141 together while disconnecting the exhaust port 159 from the port 141.

Figuref23 illustrates the valve 458. A valve stem 160 has pistons 16| and 162 which are located in a cylindei` bore 163 of the valve casing,

said cylinder bore 163 having ports 165 and 166.

The stem 169 with the pistons 16| and 162 are normally upheld by a spring 161 between the piston 162 and a cap 110. The pipe 451 is connected to a bore 11| in a cap 112 which covers the end of the cylinder bore 163. Normally the piston 162 blocks the port 166 which is connected to the pipe 459. But when pressure is exerted in the cylinder bore 163 from the pipe 451 against the end of the piston 16|, the latter and the piston 162 are shifted downwardly t0 connect the ports 165 and 166, the former being connected to the pipe 466. Thus at that time the pipes 459 and 469 are connected as previously described. When the pressure from the pipe 451 is released, the connection between pipes 459 and 460 is broken. In the cap 110 is a bore 113 connected to a drain pipe 114. This is for the purposeof discharging oil that may leak by the piston '162 into the sump. This pipe 114 is connected to the sump or oil supply tank, not shown, as are all drain pipes hereinafter mentioned.

Figure 24 illustrates the piston-cylinder unit 41| and the switch 412 in the switch box 412a.

This construction comprises a valve casing and piston-cylinder ycasing 13| and the switch box 412er, all connected together as shown. The pipe 410 is connected to a bore 182 through which is a cross bore 183 leading to a bore 164 parallel to the bore 182. The cross bore 183 merges into 'an enlarged threaded counterbore 185 which is `plugged with a screw threaded plug 189. The

cross bore` 183 further has a counterbor'e 181 in which is located a sleeve 188providingaseat for a ball 169 held in closed position by a spring 190 on a pin 19| projecting from the plug 136;

The bore 182 is furtherr intercepted by a bore 192 which merges into a larger bore 193 containing a bored plug 194 having a seat for a ball 195 held in position by a spring 196 on a pin 191 which is on the end of a spindle 198 having a threaded portion 199 in a nut 896 screwed into the casing 180. The larger-bore 193 is connected t0 the bore 184. Adjustment nuts 80| are provided on the threaded portion 199 outside the casing.

The foregoing constitutes two check valves in parallel and opening in opposite directions. However, the ball will not move away from its seat until the pressure rises to the extremely high figure already referred to, the pressure required to move the ball |95 being adjustable by adjusting the spindle 198.

On the other hand.A 'for the purpose of exhausting fluid back intothe parts 820, 82|,

:pipe 418, the ball 188 will move away from its seat 412:1 and the piston 886. In the box 412e is the switch 412 on the end of the rod 888. This is a normally open switch but when the fluid passing by the ball 195 enters the chamber 881 and moves the piston 888 downwardly, the rod 808 closes the switch 412 against terminals 848 and 8H respectively connected to the wires 818 and 8i i. A drain pipe 3|2 is connected to a bore 853 extend.- ing into the cylinder 885.

Figure 25 illustrates the valve 432 and shows this valve in the actuated position connecting the pipes 433 and 452. A valve stem S28 has pistons 82|, 822 and 823. The pipe 433 is connected to -a port 824 While the pipe 452 is connected to a port 825 and as indicated when the valve stem 820 and the pistons 82|, 822 and 823 are actuated to the right, the ports 824 and 825 are connected. The exhaust pipe 434 is connected to a channel 826 which is connected to a port 821. When the 822 and 823 are shifted to the left by a spring 828 in the valve cap 829 which `spring engages the piston 823, the piston 822 closes the port 825 and connects the port 824 to the port 821.

It will be remembered that the valve 432 is operated by a pilot valve 43| which in turn is operated by a solenoid 438. Neither in this case nor in any other case is the solenoid illustrated Vin detail since all of such solenoids are cr may bepurely conventional and the construction thereof is well known. The core of the solenoid 438 is connected to a valve stem 838 o the pilot valve 43| and it is noted that actuation of the solenoid 438 moves the valve stem 838 downwardly and Figure 25 shows valve stem 838 having been moved downwardly. The valve stem 838 has pistons 83| and 832. A port 833 is connected to the pipe 468 while a port 334 is connected to a bore 835. These two ports 833 and 834 are connected when the pilot valve is actuated as shown. Thereby fluid is admitted to the bore 835 which is intersected by a bore 83'5. In an .enlarged portion of the bore 838 is a spring actuated ball check valve 831 connecting the bore 838 to a passage 838 leading to the cylinder 839 in which the pistons 82|, 822 and 823 are located. 'An adjustable needle valve 848 is likewise located in the bore 836 and connects it to a transverse .bore 84| also leading into the cylinder 838.

- When the parts 838, 83| and 832 are in the actuated position shown in Figure 25, uid readily passes from the pipe 468 via the port 833, port 834, bore 835, bore 836, valve 831, passage 838 into the cylinder 838 to act upon the valve piston 82| to move it and the other parts to the right -as shown thus connecting the pipes 433 and 462.

When, however, the solenoid 430 is deenergized, a spring 845 moves the pistons 83| and 832 upwardly, connecting the bore 835 via port 834 to a port 848 which is connected to a drain pipe 848. At the same time the piston 832 blocks the port 833. Fluid can drain from the cylinder 838 through the transverse bore 84| and pass the needle valve 848 into the bore 836 and thence into the bore 835 into the port 834 and the port 846 fand out the drain pipe 848, but this draining is 16 controlled by the needle valve 848. wherebyto prevent shock to the valve 432 and the system in general.

Figure 26 illustrates the valve 436 which lis operated by the pilot valve 45| which is in turn operated by the solenoid 458. The valve 436 is identical with the valve 432 so the valve 43'6 need not be specically described, but it is noted-that the valve stem 828 and the pistons 82| and 822 and 823 are shown in the left hand or normal position in Figure 26. The same characters of reference are used in Figure 26 for the valve parts as were used in Figure 25 but it is noted that the port 824 is connected to the pipe 435 and the port 825 is connected to the pipe 452 while the passage 828 is connected to the pipe 431.

The pilot valve 45| has all the parts, ports and functions of the pilot valve 43| so again the same reference characters are used and the description need not be repeated. However, a bore 858 is drilled into the port 834 and this bore 868 is connected to the pipe 451. This is a feature not supplied nor contemplated by the valve manufacturer. The port 833 is connected to the pipe 456 while the port 848 is connected to va ldrain pipe 88|. rlhe pilot valve 45| functions, with respect to the valve 438 exactly as the pilot valve 43| functions with respect to the valve 432. However, the pilot valve 45| is also a main solenoid operated valve with respect to the pipes 453 and 451 for when the solenoid 458 is actuated these pipes are connected for direct flow of fluid.

Figure 27 illustrates the main valve 443, the pilot valve 442 operated by the solenoid 44| and the pilot valve 416 operated by the solenoid 415. Each of the pilot valves 442 and 416 is arranged to operate the main valve 443, the pilot valve 442 operating said main valve in one direction and the pilot valve 41'8 operating said main valve in the other direction. To hold the main valve 443 in the neutral position, a spring centering mechanism is provided which will be presently described.

The pilot vaives 442 and 418 are identical with the pilot valve 43| so the same reference characters have been used and the detailed description need not be repeated. In the case ofthe pilot valve 442, the port 845 is connected to a drain pipe 862 while in the case of the pilot valve 418, the port 848 is connected to a drain pipe 883.

The main valve 443 is itself substantially identical with the main valves 432 and 438. Accordingly, again the same reference characters have been used and the description will not be repeated. It will be seen that the port 824 is connected to the pipe 446, the port 825 is connected to the pipe 444, and the channel 828 is connected to the pipe 418 which is an exhaust pipe leading to the sump. However, in Figure 27 the pistons are marked 82|a, 822:; and 823a because they are different from the pistons 82|, 822 and 82.3 of Figures 25 and 26 in length and locus and the piston 8230i has extending from it a long stem 818. Referring now to Figure 27, the transverse bore 84| and the passage 838 of the pilot valve 418 empty into a cylinder bore 81| which merges into a larger bore 812 both located in a connect. ing member 813 connecting the casing of the pilot valve 416 with the casing of the valve 443. The bore 812 is continuous with a bore 814 in the casing of the valve 443 and as will be seen, the long stem 818 is mostly located in this bore 812-814.

Located on the long stem 818 are slotted discs with hubs 815 and 816 and extending between them are springs 811 and 818. The disc 816 is held against the springs 811 and 818 by means of a pin 819. When the valve 443 is in the mid position as shown, the disc 816 is against the right hand end of the bore 812 while the disc 815 is against the left hand end of the bore 814. Because the discs 815 and 816 are slotted, pressure fluid from the pilot valve 416 can readily reach the end of the piston 826m to move it and the parts integral with it to the left. Without further description it will readily be seen that when both solenoids 441 and 415 are deenergized, the pistons 82 |a, 822e and 823e are in the central `position shown in Figure 27 in which position all three of the pipes 446, 445 and 418 are blocked. When only the solenoid 44| is energized these three pistons are moved to the right, and when only the solenoid 415 is energized, these pistons are moved to the left. When only the solenoid 44| is energized, the port 821 is blocked which blocks the pipe 418 and at the same time the ports 824 and 825 are connected which connects the pipes 446 and 444. When only the solenoid 415 is energized, the port 825 is blocked which blocks the pipe 444 and at the same time the ports 824 and 821 are connected which connects the pipes 446 and 418.

Referring now to Figures 2 and 2l, the valve mechanism 424 consists of a check valve 895 and a throttle valve 886 connected together as shown in Figure 2. The pipe 423 branches into a. pipe 881 leading to the check valve 885 and into a pipe 888 leading to the throttle valve 886. '.llhe check valve 885 is connected by a pipe 889 to the pipe 425, while the throttle valve 886 is connected by a pipe 890 to the pipe 425. The check valve 885 allows fluid to flow through it away from the cylinder 4| 3 but not towards it. Thus the charging box 300 moves towards the mold band |35 under the control of the throttle valve 886 but the charging box 300 moves away from the mold band under other controls as will presently be explained.

The throttle valve 886 is illustrated in Figure 22 and the throttle valve 46| as well as the needle valve 449 may be of the same construction. Such throttle valves or needle valves have chambers 900 and 90| each connected to piping and separated by a wall 902 having an orince 903 adapted to be restricted by a conical plug 904 on the end of a spindle 905 having threads 996 and a wheel 901 by the tiu-ning of which the valve can :be adjusted.

The check valve 885 is illustrated in Figure 21 and the check valve 464 may have the same construction. A channel 910 is connected to piping and a channel 9| at right angles to the channel 9|0 is likewise connected to piping. A plug 9|2 is pressed by a spring 913 against a seat 9|4 at the end of the channel 9 0. Without further description it will be evident that fiuid can flow from the channel 910 to the channel 9|| but not vice versa.

.Referring again to Figure 2, the switch 503 which is in the switch box 5030. illustrated in Figure 6 and which is closed when the dog 49| is riding on the roller 595, is connected by a wire 929 to the -lline 511 and the other end of the switch 503 is connected by a wire 92| to a relay 922 which is connected by a wire 923 to the line 518. When, during the movement of the charging box 309 in or out, the dog 49| is riding on the roller 595, this relay 92 2 is therefore energized. This relay 922 operates a'switoh 924 which is connected by a wire 9,25 to the line 515. The other side of' the switch 924 is connected by i8 a wire 926 to a solenoid 921 the other end of which is connected by a wire 928 to the line 516. Accordingly, whenever the relay 922 is energized, the solenoid 921 becomes energized and conversely deenergization of the relay 912 results in deenergization of the solenoid 921.

The solenoid 921 operates a valve 936 having a valve stem 931 with three pistons as shown in Figure 2. A spring 935 keeps the valve stem 93| to the right when the solenoid 921 is deenergized. At that time the exhaust pipe 149 is connected to a pipe 936 which is connected to an exhaust pipe 931 and consequently when the charging box 300 is moving outwardly it is controlled by no valve provided the solenoid 921 is deenergized. But when the dog 99| is riding on the roller 505 the solenoid 921 is energized, which connects the pipe 149 to a pipe 939 which is connected to a valve 946 which is connected by means of a pipe 94| to the exhaust 931 and hence, if the charging box 399 is moving outwardly, it is controlled by the valve 940 which may be of the construction shown in Figure 22.

Referring now to Figures 13, 14 and 15, an angle iron 95|) is welded to the rear slanting wall 95| of the charging box 309 on the outside thereof. This angle iron 950 is detachably secured to an angle iron 952 as by means of a plurality oi' sets of screws and nuts 953. The angle iron 952 is welded to an angle iron 954 the vertical portion of which is seen in Figure 14, while most thereof which is visible in Figure 13 is the horizontal portion which has a long slot 955.

Secured tothe arm 311 as by means of screws 956 is an horizontal plate 951. The angle iron 954 is removably and adjustably secured to the plate 951 by means of screws 958 extending through the slot 955 and into the plate 951. Thus the charging box is secured to the arm 311 and is adjustable in the direction of its movement in and out relative to the arm 311.

Referring now to Figures 14 and 15, I may provide 'adjustable sliders or contactors 960 and 96|, the former at the front and rear of the box and the latter at the sides of the box. However it must be clearly understood that these sliders 960 and 96| are optional features and in the smaller sizes of presses the mechanism hereof has operated very well without any such sliders or contactors. The sliders 969 that I have used have medium hard rubber contacting strips 982 riding on the wear plate 699 (made of steel) while the sliders 96| that I fhave used have fibre contacting strips 963 riding on the wear plate 389. These sliders with their wear strips have given excellent results in actual practice.

The sliders 960 and 96| are adjustably attached to the bottom of the charging box 390. As shown, supporting plates 965 are welded to the narrow sides of the charging box 309, and between them extend front and back supporting plates 966 welded to the edges of the plates 965 in cut-out portions thereof as indicated in Figure 14. Threaded studs 961 are secured to and extend from the supporting plates 965 966 and through vertical slots in the sliders 960 and 96! and thus the sliders can be adjusted vertically and then secured in position by nuts 969 on the studs 961. For further convenience in leveling this mechanism and for ensuring a oontinuous contact between the wear plate 369 and the contacting strips 962 and 963, I provide leveling bolts 919 extending through shelves 91| extending from the supporting plates 965 which can be made to Contact the sliders 989 and can 19 be used to raise and lower the charging box 399 relative to the wear plate 389 so that the former will bear upon the latter with just enough pressure and never too much in order to keep the mix from escaping except into the mold and in order to avoid excessive wear on the wear plate 389. It has been found that, in the manufacture of certain white vitried grinding wheels, a charging box having a metal bottom suffers enough U bolts 91| can be used to lock them in place to assist in supporting the box 399.

In shape the charging box 399 may be said to be a hollow right prism with an open top and open bottom continued downwardly by a hollow right prism with an open top and bottom, the rear face of the lower prism being continuous with the rear face of the upper prism and the front faces of the prisms forming an obtuse dihedral angle. This results in an open bottom which is rectangular and the ratio of the length to the width of the rectangle is large. It also results in a forward slant to the bottom of the charging box so that, when the box is away in" and is reversed, inertia assists gravity in delivering the mix into the mold. The length of the rectangular opening in the bottom of the box is greater than the diameter of the mold band |35 so that the mold can be filled level. I have found that a charging box of this shape well fills a mold when the box 309 and bottom plate |19 move relatively to each other in any of the ways hereinafter explained, but some of the features of the box are more a matter of convenience than a functional necessity, for example the bottom opening does not have to be a rectangle, it could be a figure bounded by a pair of concentric sectors of generous radius, but such a box would be more difcult to manufacture.

Referring now to Figures 13 and 19, extending from the side of the table |20 is an extension 915 which supports a post 916 on which is clamped a horizontal arm 911 having a split end through which extends a clamping screw 918 tightened by a hand wheel 919. It is clear that the horizontal arm 911 can be raised and lowered and also angularly adjusted on the post 916. The tube 303 is integral with the arm 911 and thus the hopper 30| is supported.

The hopper 39| may have any funnel shape but actually it was an inverted foursided truncated pyramid. As shown in Figure 13, the cylinder 348 is attached to the arm 911 by means of bolts 980.

As shown in Figure 19, above the hopper 39| is a feeding chute 983 having an adjustable extension 984. This chute 983 is supported by a bracket 989 secured to the cap ill. A feeding hopper 991 which can have any convenient shape is removably secured by metal straps 998 having hook portions 989 in the top thereof by means of which the hopper 981 can be hung on a rod 999 supported overhead in any suitable manner. This hopper 991 is one of many of the same kind so that as fast as one gets empty a full one can be substituted therefor. A combination spout member and closure 99| is hinged to the hopper 981 by pins 992 to open and close the hopper 981. As shown in Figure 19, the spout and closure member 99| is in open position, but when it is swung away from the plane of the drawing a portion with no orice covers the opening in the bottom of the hopper. Details such as these may be varied at will, the arrangement shown providing a considerable quantity of mix in the pipe line with provisions for bringing in new supplies of mix as desired.

Referring now to Figures 16, 17 and 18, the apparatus of this invention is versatile and it is possible to cause the mold filling operation to operate in several different ways. In this connection a sequence of motions in a certain relative order may give excellent results for the manufacture of grinding wheel out of a certain dry granular mix having a particular angle of repose. Furthermore there are many grit sizes of abrasive and proportions of bond to abrasive and also the abrasive may be silicon carbide or aluminum oxide and there are several varieties of the latter. The shape of the granules vary widely and is signicant. Furthermore the bond may vary between resinoid bond on the one hand andvitried bond on the other hand and there are dozens of varieties of each. Therefore my invention, in providing a mechanism which can be changed, not only to adjust the exact time of the occurrence of a particular action but also to change the order of occurrences of events, presents decided advantages. Furthermore the provision of a long, generally rectangular, opening to the charging box, the length of the rectangle being substantially radial to the arc of movement thereof together with the slow movement of the charging box over the mold cavity, appears to present outstanding advantages in mold iilling as proved by actual experience. In this connection the retreating edge of the charging box, as represented herein by the front contacting strip 952 and its slider 960 constitutes a leveling device for leaving the mold filled level without any depressions or elevations therein.

Referring now to the above mentioned Figures 16, 17 and 18 and also referring to Figures 6, '1 and 8, the box 499a can be positioned relative to the box 502a so that the dog 492 hits the roller 491 well in advance of hitting the roller 569. The rst action causes the lower mold plate |10 to start to descend. In Figure 16 this plate started to descend just as the charging box 300 came to the arbor |12. The charging box 3D0 went a little beyond the mold and was then reversed and before it had reached any portion of the mold band |35 on the return trip the plate |19 was all the way down. As it retreated slowly over the mold cavity the mold was well lled and leveled, The valve 940 was so adjusted that the charging box 309 went slowly enough thoroughly to iill all parts of the mold. It may be said that the orifice of the charging box, as it moves across the mold, intersects the circle of the mold band |35 in an infinite number of narrow areas which collectively cover the entire area of the mold band and furthermore overlap each other. In this way the entire area of the mold band is covered and there is a charge of dry granular mix with a. good pressure head behind it ready to fall into the cavity exposed and to fill all parts thereof equally. The particular advantage, especially with sticky mixes, of causing 

